Wireless communication devices such as cellular radiotelephones transmit and receive radio frequency (RF) communication signals from a fixed base station associated with a communication system, such a cellular radiotelephone communication system, PCS network, paging network or other communication network. While conventional wireless communication devices transmit RF signals and receive RF signals by way of an integral antenna, it may be desirable to transmit the RF communications signals external to the device, such as to an external antenna, by way of a hard-wired connection. For example, a cellular radiotelephone may be physically coupled to a charging cradle installed in a vehicle to provide coupling of RF signals to a separate high power transceiver and an external antenna.
Conventional wireless communication devices have incorporated an external input/output (I/O) port for transmitting RF communication signals to the charging cradle or other external device. When transmitting RF communication signals within a printed circuit board of the wireless communication device such as from a transceiver to the I/O port, the printed circuit board must be properly designed to minimize signal loss and interference from other signals and provide the proper impedance matching. That is, the location of the transmission lines within in the layers of the printed circuit board should be chosen depending upon, among other factors, the number of layers of the printed circuit board, the location of ground planes and components, the selection of dielectric materials or housings. Although there are numerous arrangements, one common arrangement for the transmission of communication signals includes a stripline construction wherein the transmission line is covered on either side by a ground plane. Another common arrangement for transmitting RF communication signals within the printed circuit board is a microstrip transmission line having a transmission line on the surface of a dielectric layer whose bottom surface is covered by a ground plane. Although the microstrip has fewer layers and is therefore thinner, this construction generally provides less isolation. In either case, the transmission line is designed to create a 50 ohm impedance to provide the proper matching to transfer signals between the wireless communication device and an external device by way of the I/O port.
In coupling RF communication signals to an external device by way of the I/O port, the RF communication signals must be transmitted from the transmission line with minimal loss of signal. Prior art devices have used conventional coaxial connectors exposed in the I/O port of the telephone adapted to mate with a corresponding exposed coaxial connector in the connector portion of an external device such as a charging cradle or a cable adapted to be coupled to an external device. Coaxial cables have previously been required to reduce RF interference at the receiver of the wireless communication device. However, such coaxial cables at the I/O port often require additional space than a conventional connector not having a coaxial cable. That is, the mating portion of the connector in the I/O port or associated with the external device is generally thicker. Also, such connectors can be generally more costly and more susceptible to damage over time.
Accordingly, there is a need for a method and apparatus having a reduced size for coupling radio frequency signals from a wireless communication device to an external port. There is also a need for durable, low cost apparatus for coupling radio frequency signals from a wireless communication device to an external port.